About 190 governments met in Lima on Monday amid hopes that a U.N. deal to slow climate change is within reach for 2015 despite warnings that time is fast running out to keep global warming within safe limits.

Cooperation between China and the United States, the top two greenhouse gas emitters, and a decision by the European Union to cut its emissions have given a new sense of momentum to United Nations talks that have failed produce agreement on a global deal in two decades.

“We've received some very positive signals,” Peruvian Environment Minister Manuel Pulgar Vidal told delegates at the opening of the Dec. 1-12 talks in a tent city at a military headquarters in Lima.

Delegates are due to work out elements of a deal to combat climate change, for a summit in Paris in a year's time, as part of a goal of limiting average world temperatures to 2 degrees (3.6 Fahrenheit) above pre-industrial times.

Temperatures have already risen by about 0.9 C (1.5F) and a U.N. panel of climate scientists says there are risks of irreversible impacts, ranging from damage to coral reefs to a meltdown of Greenland's ice that would raise sea levels.

The talks have a new sense of hope for at deal, despite falling oil prices that complicate a shift to renewable energy, after the United States last month agreed to cut emissions by 26 to 28 percent below 2005 levels and China agreed to set a cap on its soaring emissions by around 2030.

The European Union also aims to cut emissions by 40 percent below 1990 levels. That means that nations accounting for more than half of world emissions have set goals.

“We need more countries to come forward” with plans for cuts, said Elina Bardram of the European Commission.

But temperatures are on track to rise above 2C.

“We are currently en route to three to four degrees Celsius (5.4 to 7.2 F) of warming,” said Tony de Brum, foreign minister of the Marshall Islands, saying it would be “disastrous” for the world.